1. Field of the Invention
The present invention relates to a cushion device used for a suspension in a vehicle. The present invention more specifically relates to a cushion device that generates a damping force according to the displacement of a piston.
2. Description of the Background Art
A vehicle such as a motorcycle is provided with a suspension. The suspension supports the front or rear wheel of the motorcycle. By the function of the suspension, force applied on the front or rear wheel is absorbed and impact applied on the vehicle is alleviated.
The suspension includes an arm that supports the wheel and a cushion device that supports the arm. The cushion device includes a combination of a spring and a shock absorber. Alternatively, an air spring is used instead of a metal spring.
The shock absorber includes a piston and a cylinder. As the piston moves in the cylinder against the spring force, the shock absorber is compressed. When the piston moves in the cylinder, the movement of the piston is supplied with resistance by oil in the cylinder.
In the disclosure of JP 5-38434 U, a shock absorber generates a damping force depending on the position of a piston. The shock absorber includes an accumulator that accumulates oil outside the shock absorber. Oil discharged to the accumulator from the shock absorber is provided with resistance when it passes through a damping force generator.
More specifically, pressure is applied on a spring provided at the outer circumference of the shock absorber as the piston moves. When the pressure upon the spring increases and the support portion of the spring is displaced, the displacement is transmitted to a valve through a cushion member. As the displacement of the piston increases, the displacement of the cushion member increases and greater resistance is applied on oil passed through the valve.
In this way, the shock absorber disclosed by JP 5-38434 U generates a damping force depending on the position of the piston. However, the valve is controlled based on the displacement of the cushion member, and therefore the range of the damping force to be generated is not wide.